1. Field of the Invention
The present invention relates to an image pickup apparatus for picking up images using a solid-state image pickup device. More particularly, the present invention relates to an image pickup apparatus including an auto-bracket function for continuously capturing a plurality of pickup images to which different image-pickup conditions are applied in sequence and an automatic adjustment function for automatically determining the optimum image-pickup condition to pickup an image, and to a method of controlling image pickup and a program.
2. Description of the Related Art
An image-pickup apparatus, such as a digital still camera picking up images using a solid-state image pickup device, etc., often has a function of automatically adjusting focus, brightness, hue, etc., appropriately at image-pickup time. For example, AF (Auto Focus), AE (Auto Exposure), AWB (Auto White Balance), etc., are typical automatic adjustment functions. Also, the apparatus is commonly equipped with a function of automatically going off electronic flash light only when an object of image-pickup is in the dark.
Some of known image-pickup apparatuses perform an operation of obtaining control values by the above-described automatic adjustment functions when a user half-presses the shutter-release button using a shutter-release button having two states, namely, a “half-pressing” and a “full-pressing”. A half-pressing of a shutter-release button is called a “half-release”, etc. In such an image-pickup apparatus, for example, the following procedure is performed for picking up images. In this regard, the AF function is taken for example here.
First, when the shutter-release button is half-pressed, the AF function is activated, the focus lens is moved with capturing pickup images continuously, and the evaluation values of a degree of focussing are obtained from the captured signals. The lens position with the largest evaluation value is the focused position. When that position is obtained and the focus lens is moved to that position, the completion of the automatic adjustment is notified by a screen display and a sound, etc. Thus, the user full-presses the shutter-release button to make it possible to record the pickup image in focus into a recording medium. In such an image-pickup apparatus, when the shutter-release button is full-pressed at once without going into a half-release state, the above-described automatic adjustment functions is not activated, the image-pickup signal is captured on the image-pickup condition at that time without change to record it into a recording medium. Alternatively, in some of the image-pickup apparatuses, even if full-pressed, a pickup image is not recorded into the recording medium until the optimum control value is obtained by the automatic adjustment function.
Here, if the automatic adjustment function is activated at half-release time as described above, there is a problem in that it takes some time until the optimum image-pickup condition is obtained, thereby losing chances of taking a picture. Also, there is a problem in that the control value determined to be the best by the image-pickup apparatus might be different from the user's intention because of the performance limit of the automatic adjustment. Accordingly, up to now, an increase in the speed of the automatic adjustment and an improvement in the adjustment performance are demanded.
In order to solve these problems, there has been an image-pickup apparatus having a function called “auto-bracket” which continuously records a plurality of images on different image-pickup conditions in a short time when a shutter-release button is pressed once. As a commonly-used auto-bracket function, a function for picking up images by changing the amount of exposure adjustment using an AE function is known. By such a function, a user can make his or her choice from a plurality of recorded images afterward, and thus it has been possible to obtain an image in accordance with the user's intention without losing chances of taking a picture. However, at the same time, there has been a drawback in that a recording medium is used wastefully. On the other hand, for example, there has been a digital camera (for example, refer to Japanese Unexamined Patent Application Publication No. 2004-135029 (paragraph numbers [0047] to [0065], FIG. 3)) in which focus-evaluation values are calculated for individual images picked up with changing the focus-lens positions by the auto-bracket function and the image with the highest value is automatically selected and recorded into a recording medium.
Also, in an image-pickup apparatus having an auto-bracket function, it is possible to change an image-pickup mode using the auto-bracket and a usual image-pickup mode which picks up an image one by one. Furthermore, it is thought that a plurality of kinds of adjustment values are changed when the auto-bracket function is activated and that the combination thereof is allowed to be set in accordance with a user's operation. By these functions, it becomes possible to pick up an image more suited to user's intention. However, the number of user operation steps increases that much. On the other hand, there has been an electronic still camera in which the auto-bracket function is automatically determined to be necessary or not based on the picked-up images, and if necessary, images are picked up using the auto-bracket function to record a plurality of images on different image-pickup conditions into a recording memory, thereby improving the operationality (for example, refer to Japanese Unexamined Patent Application Publication No. 2001-8087 (paragraph numbers [0020] to [0034], FIG. 1)).
As described above, as the technique disclosed in Japanese Unexamined Patent Application Publication No. 2004-135029, by automatically selecting the image with the optimum image-pickup conditions out of the pickup images by the auto-bracket function and recording it into a recording medium, it is possible to use the recording medium effectively, and to increase the possibility of obtaining the image preferable to the user without losing chances of taking a picture. Also, by finely adjusting the image-pickup conditions at auto-bracket time, it becomes easy to reflect the user's intention. As the technique disclosed in Japanese Unexamined Patent Application Publication No. 2001-8087, by automatically determining the necessity of the auto-bracket function, it is possible to further increase the operationality of the user.
However, the technique for automatically keeping images in a recording medium and the technique for automatically determining the necessity of the auto-bracket function are basically the same as an automatic adjustment technique at half-release time described above, and thus there remains a possibility of recording images which are not in accordance with the user's intention. The advantage of the auto-bracket function lies in the fact that the images preferable to the user can be selected by that user from a plurality of recorded images after picking up images. Thus, that advantage is sometimes lost if the above-described automatic selection and automatic determination are performed.
On the other hand, if the auto-bracket function is used, it is commonly necessary to change the operation modes by a key operation, etc. A large number of users pick up images in an operation mode in which an automatic adjustment function is activated at ordinary use time, and use the auto-bracket function by changing the operation mode if necessary. However, in such a way of use, the user often loses a chance of taking a picture while changing the operation modes. In spite of this, if the auto-bracket function is activated all the time, even in a case of obtaining an appropriate image by the automatic adjustment function, a lot of images are recorded, the capacity of the memory is used unnecessarily, and it takes time and effort to select necessary images. That is to say, in a known image-pickup apparatus, there has been a problem in that the operationality for a user of using the auto-bracket function at once when necessary has not been considered and the advantage of the auto-bracket function has not been utilized.